Electronic data processing equipment employing microelectronic circuitry requires regulated DC voltages for circuit operation. The desired DC voltage is obtained from a high voltage DC source by means of regulators with the regulated DC voltage requirements for EDP equipment tending more and more towards lower voltages and higher currents. For example, currents in kilo-amperes are being used at voltages as low as 3.3 volts DC. At these power levels, the efficiency of the power supplies becomes an important consideration.
The achievement of high electrical efficiency in EDP power supplies is complicated by the trend toward lower regulated voltage requirements. In switching voltage regulators, for example, which employ transformers and rectifiers for DC voltage regulation, the output circuit rectifiers account for a major part of the regulator power losses. Typically, these devices are fast recovery silicon rectifiers which exhibit a forward voltage drop of about 1.5 volts, or about half the value of the regulated output voltage. Consequently, the silicon rectifiers produce regulator power losses approaching half the value of the regulated output power.
Another rectifying device, the hot carrier or Schottky barrier diode, is now available and exhibits a forward voltage drop of only about 0.5 volt, as contrasted to the 1.5 volt drop of the silicon diode. While the device has been successfully employed in low power switching regulators, the reverse voltage limitation of the hot carrier diode prevents its use in many conventional high power switching regulators. The silicon diode can withstand reverse voltages of up to 45 or 50 volts, while the hot carrier or Schottky diode is limited to about 35 volts. In a conventional high current switching regulator employing linear reactors, as disclosed in U.S. Pat. No. 3,573,597, the operating voltages experienced by the output diodes are in excess of reverse voltage limitations of the hot carrier diode.